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Electrochemical Method to Measure the Defect-Free Zone in Silicon Wafers

IP.com Disclosure Number: IPCOM000047210D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Cazcarra, V: AUTHOR [+2]

Abstract

There is a real need in the semiconductor industry to investigate defects that may create leakage currents in the proximity of the active surface of the wafers (0 to .7 mm depth). Existing solutions such as beveling or MOS retention time techniques are complicated because they necessitate special preparation of the wafers, and are expensive. The present electrochemical method, based on a dissolution step with an efficient etching solution, allows one to reach the surface where defects can exist. The electrical activity of those defects can be evaluated immediately by the measurement of leakage current (cathodic current). The proposed method is basically comprised of two steps: 1) dissolution of silicon, and 2) measurement of the electrolytic reverse current.

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Electrochemical Method to Measure the Defect-Free Zone in Silicon Wafers

There is a real need in the semiconductor industry to investigate defects that may create leakage currents in the proximity of the active surface of the wafers (0 to .7 mm depth). Existing solutions such as beveling or MOS retention time techniques are complicated because they necessitate special preparation of the wafers, and are expensive. The present electrochemical method, based on a dissolution step with an efficient etching solution, allows one to reach the surface where defects can exist. The electrical activity of those defects can be evaluated immediately by the measurement of leakage current (cathodic current). The proposed method is basically comprised of two steps: 1) dissolution of silicon, and 2) measurement of the electrolytic reverse current. When a P type silicon wafer is immersed in a suitable electrolyte contained in an electrochemical cell and then is anodically (+) biased, the silicon will dissolve. The depth of the depression is proportional to the anodic etching time at a given current density (Fig. 1). A mixture of CH3CH2OH, HF and HNO3 has demonstrated its value for etching a defined area of silicon (1 cm2). In the second step, the silicon wafer is biased cathodically (-) in a 5% hydrofluoric acid solution. The change in the electrolytic reverse current is monitored by comparing the measurements effected at the surface without dissolution and in the depression after...